Isabella I of Jerusalem

Isabella I (Old French: Ysabel; c. 1172 – 1205) was the queen of Jerusalem who reigned from the early 1190s to her death. She received the homage of her vassals as the rightful heir to the throne after the death of her half-sister Queen Sibylla in 1190, but Sibylla's widower, Guy of Lusignan, held onto the kingdom until 1192. Isabella became queen upon her coronation in 1198. Having little political ambition, she passed the government on to three successive husbands, Conrad of Montferrat, Henry II of Champagne, and Aimery of Lusignan, all of whom included her in the issuing of their charters. Isabella's co-reign with Aimery saw the compilation of the Livre au Roi, a law treatise establishing the rights and obligations of queens regnant of Jerusalem.

Isabella was the daughter of King Amalric and his second wife, Maria Komnene. After Amalric's death in 1174, Queen Maria married Balian of Ibelin. The marriage of Amalric's elder daughter, Sibylla, to the controversial Guy of Lusignan divided the nobility in two camps, with Isabella's stepfamily opposing Guy. Isabella's half-brother King Baldwin IV arranged for her to marry the lord Humphrey IV of Toron, whose family supported Guy and opposed the Ibelins. Baldwin IV suffered from leprosy and could not sire an heir; he named Sibylla's son, Baldwin V, as his successor. The High Court stipulated that a committee of Western European rulers was entitled to decide whether Sibylla or Isabella should inherit the throne if Baldwin V died. When Baldwin V died in 1186, Sibylla seized the throne before the committee could choose. Guy's opponents wished to install Isabella as anti-queen, but her husband, Humphrey, recognized Sibylla and Guy as rulers.